1. Field of the Invention
The present invention relates to serialization of microprocessors and, more particularly, to providing a microprocessor serial number on a programmable fuse.
2. Description of the Relevant Art
For some time, workstations, mini-computers, and mainframes have had serial numbers embedded in them which uniquely identify them. Addition of the serial number allows a manufacturer to trace a product in the field back to the original equipment manufacturer (OEM). This allows the manufacturer greater control over its product. In addition, provision of the serial number permits independent software vendors to register their products. By serializing software to a given work station, mini-computer, or mainframe, the independent software vendors can thereby minimize or prevent unauthorized use and/or copying of their products. Microprocessors and personal computers, however, typically have not been tracked by serial number because of the added expense of providing circuitry to store and/or read the serial number. The cost of such circuitry in work stations, mini-computers and mainframes is generally not significant compared to the overall cost of the system and the potential revenue available from serializing the software.
However, as the complexity of microprocessors used in personal computers has increased, it is becoming increasingly cost-effective to provide additional circuitry on the wafer (and corresponding process steps in the manufacture) to provide a serial number. Moreover, as the cost of developing software for personal computers increases, it is increasingly desirable to serialize software to a particular machine, such that when installed on a particular processor the software may read the password or serial number and thereafter be uniquely keyed to that particular processor. An attempt to install the software on a different processor would fail. Accordingly, there is a need for a cost effective and efficient way of providing a unique serial number with a microprocessor in order to trace a product in the field back to an original equipment manufacturer.
As discussed above, it is desirable to serialize software to the microprocessor by means of integrating a serial number into the wafer. One problem, however, with doing so, is that if the processor is upgraded, or otherwise replaced, the software will cease to function since, to the software, there is no difference between being loaded onto an unauthorized computer system and having an unauthorized processor provided to it. In either case, the software will be keyed to a processor that is no longer present and will not function. Accordingly, what is needed is an upgrade method whereby serialized software can detect if it is running on an unauthorized processor and in response thereto, initiate a reauthorization process. If the reauthorization process is successful, the software will function on the upgrade processor. Failure of the reauthorization process, however, will mean that the software itself is loaded on an unauthorized system, and hence, will not function.